1. Field of the Invention
The present invention relates to a seal device disposed in crawler roller, reduction gear, hydraulic motor, track roller or the like. More particularly, the invention relates to a seal device for crawler roller, hydraulic motor or the like used in construction machinery, which provides an effective seal against a process.
2. Description of the Related Art
There is a seal device of a mechanical seal type as a prior art related to the present invention which is employed in a crawler unit. This seal device is installed between a casing and a rotary member in order to keep out slurry, dirt, water containing abrasive particles or the like from the relatively rotating interface therebetween. This, however, necessitates use of a resilient O-ring for providing a seal between a seal ring of the seal device and the casing which retains the seal ring in a mating manner. Abrasive particles entrapped between the seal ring and the casing are likely to cause rapid wear of the seal ring and the casing. Wear of an urging spring for the seal ring and immersion of the spring in the dirt due to the abrasive particles will lead to an insufficient urging force against the seal ring. To alleviate these problems, resilient rings are introduced to provide not only a resilient force to the seal ring but also a seal at the interface between the contact surfaces where the seal ring is retained.
Primary related art of the present invention is found as a floating seal disclosed in U.S. Pat. No. 6,086,069 issued to Bedford as shown in FIG. 9. This illustrates a cross sectional view of a floating seal 101 mounted in a crawler roller unit. In FIG. 9, a reference numeral 120 represents a shaft. The shaft 120 is disposed within a through bore of a roller 125, and a floating seal 101 is disposed in the gap formed between the shaft 120 and the roller 125. The floating seal 101 provides a seal by preventing dirt water or fine dirt particles from entering thereto.
In this floating seal 101, a first resilient ring 102 has an annularly shaped body whose cross section is “J”-shaped and outer surface forms a curved concave face 105. One end face of the primary resilient ring 102 is defined as outer fitting face 102A while the other end face is defined as inner fitting face 102B. Likewise, a second resilient ring 103 has also an annularly shaped body whose cross section is “J”-shaped and outer surface forms a curved concave face 105. Therefore one end face of the secondary resilient ring 103 defines outer fitting face 103A while the other end face defines inner fitting face 103B.
Next a first seal ring 110 has an annularly shaped body whose cross section is “U”-shaped and its radially extending end face of the first seal ring 110 defines a seal face 110A. An annular groove of the seal ring 110 which is located on the other side of the seal face 110A defines a mount groove portion 110B. Likewise, a second seal ring 111 has an annularly shaped body whose cross section is also “U”-shaped and its radially extending end face of the second seal ring 111 defines a mating seal face 111A. An annular groove disposed on the other side of the seal face 111A then defines a mount groove portion 111B.
The first resilient ring 102 and the second resilient ring 103 thus constructed as well as the first seal ring 110 and the second seal ring 111 are all installed within the chamber formed between the shaft 120 and the roller 125, as depicted in FIG. 8. Therefore the first resilient ring 102 and the second resilient ring 103 retain curved concave surfaces 105, 105 relative to an ambient passage chamber 126. Also the first resilient ring 102 and the second resilient ring 103 possess curved convex surfaces relative to a lubricant-filled internal chamber 127. The first resilient ring 102 exerts a resiliently urging force such that the seal surface 110A of the first seal ring 110 is pressed against the second seal ring 103. The opposed seal surfaces 110A and 111A being pressed against each other provide an effective seal for the process fluid coming into the ambient passage chamber 126.
When the first pressure receiving surface 105 of the first resilient seal ring 102 and the second pressure receiving surface 105 of the second resilient seal ring 103 are acted on by the sealed fluid from the ambient communication chamber 126 side, the first pressure receiving surface 105 of the first resilient seal ring 102 and the second pressure receiving surface 105 of the second resilient seal ring 103 which are bent to form concave surfaces are further bent toward the internal chamber 127 side due to the fluid pressure. This causes the contact forces at the first seal surface 110A and the second seal surface 110A to decrease. At the same time, this also induces elastic deformation of the first resilient ring 102 and the second resilient ring 103 in such a direction that the first inner circumferential mount portion 102B of the first resilient ring 102 and the second inner circumferential mount portion 103B of the second resilient ring 103 may depart from the first mount concave portion 110B and the second mount concave portion 111B, respectively. As a result, seal ability at the first mount concave portion 110B and the second mount concave portion 111B is weakened. Furthermore, sealed fluid or fine dirt particles entering from the ambient communication chamber 126 side into the interface gap formed between the first inner circumferential mount portion 102B and the first mount concave portion 110B and another gap between the second inner circumferential mount portion 103B and the second mount concave portion 111B will cause wear of the contact surfaces of the first inner circumferential mount portion 102B and the second inner circumferential mount portion 103B. This will lead to a deterioration of the seal performance in the floating seal 101.
In particular, the first seal ring 110 and the second seal ring 111 are resiliently urged against each other by the first resilient ring 102 and the second resilient ring 103, respectively. In this configuration, elastic deformation of the first resilient ring 102 and the second resilient ring 103 causes the contact force between the first seal surface 110A of the first seal ring 110 and the second seal surface 111A of the second seal ring 111 to decrease. Such elastic deformation also causes the first seal surface 110A and the second seal surface 111A being in contact to
Moreover, there is another type of floating seal disclosed in U.S. Pat. No. 5,826,884 issued to Anderton. For the track seal assembly disclosed therein, a loading member corresponding to a resilient ring is arranged to urge a ceramic seal member against a seal surface, similarly to the descriptions in FIG. 9. Thus there remain similar problems encountered in FIG. 9.
The present invention is introduced to alleviate the above mentioned problems. A primary technical goal which this invention tries to achieve is to provide a seal ring with a desired urging force by means of a resilient seal ring and to exhibit seal capability of a seal surface by sealingly retaining the seal ring even under the influence of pressure of dirt water or the like. Another goal is to prevent dirt water or the like from leaking to the interface between the resilient seal ring and the support portion by sealingly retaining the seal ring with the resilient seal ring. Yet another goal is to prevent dirt water or the like from giving damage to the mount surfaces of the resilient seal ring.